Influence of quench on ageing response and mechanical properties of Al-Zn-Mg-Cu-Zr alloy
(Analysis and Measurement Center, Harbin Institute of Technology, Harbin 150001, China)
Abstract: The effect of quench rate and transfer time on the precipitation sequence and mechanical properties of an Al-Zn-Mg-Cu-Zr alloy was investigated. A consistent trend of the decrease of ductility with the decrease of quench rate and the increase of transfer time was observed. This is attributed to the quench-induced precipitates of equilibrium MgZn2 phase formed along subgrain and grain boundaries, which promotes the intergranular fracture. The strength decreases greatly when the transfer time is over 90s, resulting from the heterogeneous precipitation on dispersoids or dislocations. The quench water temperature has a little influence on the evolution of matrix precipitates and strength. This alloy exhibits less quench sensitivity.
Key words: Al-Zn-Mg-Cu-Zr alloy； quench； ductility； strength